Redshift
In physics, redshift is a phenomenon where electromagnetic radiation from an object undergoes an increase in wavelength. Examples of redshifting are a gamma ray perceived as an X-ray, or initially visible light perceived as radio waves. Redshifts are also seen in the spectroscopic observations of astronomical objects. A special relativistic redshift formula can be used to calculate the redshift of a nearby object when spacetime is flat.
About Redshift in brief
In physics, redshift is a phenomenon where electromagnetic radiation from an object undergoes an increase in wavelength. Examples of redshifting are a gamma ray perceived as an X-ray, or initially visible light perceived as radio waves. The opposite of a red shift is a blueshift, where wavelengths shorten and energy increases. Redshifts are also seen in the spectroscopic observations of astronomical objects. A special relativistic redshift formula can be used to calculate the redshift of a nearby object when spacetime is flat. In many contexts, such as black holes and Big Bang cosmology, redshifts must be calculated using general relativity. The history of the subject began with the development in the 19th century of wave mechanics and the exploration of phenomena associated with the Doppler effect. In the early 1900s, Vesto Slipher discovered that most spiral galaxies, then mostly thought to be spiral nebulae, had considerable redshifted. Subsequently, Edwin Hubble discovered an approximate relationship between the velocities of such spirals and the distances to them with the formulation of his eponymous Hubble’s law. These observations corroborated Alexander Friedmann’s equations in 1922, which he derived from Friedemaître–Lemaîîn’s equations in 1923. In 1924, the Lowell Observatory discovered that the great spiral Andromeda had the quite exceptional velocity of 300 km –300 km per year. In 1926, the Hubble telescope found that all but three of the 15 spiral neBulae spread across the entire celestial sphere, all but one of them having three positive redshift.
In 1927, the first redshift was observed in the Crab Nebula, which is now considered to be one of the most luminous galaxies in the universe. The term redshift has been used to develop several terrestrial technologies such as Dopplers and radar guns. It is also used to refer to a type of radar gun called a radar reflector, which can detect objects in the air at a distance of up to 1,000 miles (1,500 kilometers) from the Earth. The word redshift does not appear unhyphenated until about 1934 by Willem de Sitter, perhaps indicating that up to that point its German equivalent, Rotverschiebung, was more commonly used. The earliest occurrence of the term red-shift in print appears to be by American astronomer Walter S. Adams in 1908, in which he mentions \”Two methods of investigating that nature of the nebular red- shift\”. The word does not seem unhypheated until around 1934, when it is used to describe the phenomenon of redshift in the early 1930s and 1940s. It was first used in a paper by the American astronomer William Huggins in the journal Astronomy and Astrophysics, which was published by the University of California, Los Angeles, in the spring of that year. There are three main causes of red shifts in astronomy and cosmology:
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This page is based on the article Redshift published in Wikipedia (as of Dec. 06, 2020) and was automatically summarized using artificial intelligence.
